1. Field of the Invention
This invention relates to a method of cleaning a dust separator which has a raw gas shaft, through which raw gas flows from the top to the bottom, and filter elements protruding into the raw gas shaft transverse to the raw gas flow, by which filter elements the raw gas is deflected into a clean gas shaft under a corresponding separation of dust, and which filter elements are briefly subjected to compressed air one after the other for blowing off the dust particles deposited thereon into the raw gas shaft, where during the application of compressed air onto the filter elements their flow connection to the clean gas shaft is interrupted, as well as to an apparatus for performing the method.
2. Description of the Prior Art
In dust separators with a raw gas shaft, which accommodates filter elements, usually filter cartridges, that are connected to a clean gas shaft, the dust-laden raw gas introduced into the raw gas shaft flows through the filter surfaces into the filter elements, from where they are sucked off as clean gas via the common clean gas shaft. To be able to remove the dust particles retained during the passage of raw gas from the filter surfaces during the operation of the filter, it is known to briefly subject the clean gas shaft to compressed air in certain intervals, so that by means of the pulses of compressed air in the individual filter elements the dust particles are blown off from the filter surfaces of the filter elements into the raw gas shaft. To prevent in this connection that the dust particles blown off from the filter elements have to be discharged from the raw gas shaft in downward direction against the raw gas stream usually passed through the raw gas shaft from the bottom to the top, the filter elements of a known dust separator are arranged in groups one above the other in a horizontal orientation, so that in the case of a raw gas flow inside the raw gas shaft from the top to the bottom the coarse-grained fraction of the dust that has been blown off can be moved downwards by the raw gas stream. This is possible because the coarse-grained fraction of the dust is accelerated when it is blown off and due to its inertia is moved away from the filter surface so far that in the case of a flow reversal by the raw gas fraction again flowing through the filter surface after the pulse of compressed air, it is no longer attached to the cleaned filter surface. Due to the friction behavior relevant for the movement of the fine fraction of the dust, which is characterized by a small Reynolds number (e.g. Re.sub.particle &lt;30), the movement of the fine dust particles is substantially determined by the gas flow. This means that the fine dust particles, which were blown off from the filter surfaces by the pulse of compressed air only to a comparatively small extent, are again attached to the filter surfaces of the filter elements by means of the raw gas stream directly subsequent to the pulses of compressed air, which leads to an increasing pressure loss and thus to a decreasing filter performance with the result that after certain operating periods the dust separator must be shut off for cleaning the filter elements. By means of a scavenging air flow through the filter elements against the raw gas flow the fine dust fraction can naturally be blown off from the filter surfaces of the filter elements and be discharged from the raw gas shaft without raw gas flow, but not during the operation of the filter.
Moreover, it is known (DE 31 11 502 A1, DE 43 34 699 C1) to block the filter elements against the clean gas shaft during the application of compressed air. Filter elements vertically lying one above the other are combined to groups, so that in the vicinity of such vertical group of filter elements there cannot be formed a raw gas flow from the top to the bottom. To make things worse, the filter elements which are disposed laterally beside the filter elements vertically lying one above the other and subjected to compressed air are likewise separated from the clean gas shaft during the application of compressed air onto the filter elements lying therebetween, which prevents the formation of a suction flow in the vicinity of these filter elements disposed one beside the other. This means that merely the coarse-grained fraction of the dust blown off can be discharged downwards due to a corresponding sinking speed, but not the fine-grained fraction, which during the subsequent connection of the filter elements to the suction of the clean gas shaft is again sucked towards the filter elements.